Refrigeration



Patented May 6; 1 941 momron Alfred o. oro, Chicago, na; algor ta" m noove- Company, North Canton, ohio, a corporatio of Ohio Application May 22, 1939, sei-isi No. 274369' 14 claim. (Ci. cz-nas) This inv'ention relates to the art of refrlgera. tion 'and more particularly to a novel three-fluid absorption refrigerating system. i\

In previous three-fluid absorption refrigerati ing systems it is customary to supply liquid l'e-` frigerant to an evaporator through which the liquid flows in a thin stream in contact with a gas stream. This possesses the disadvantage that small as the stream of liqui'd flowing through v o the area of liquid to metal contact is extremely the 'evaporator amounts only to a ,thin trickle. Also the area of gas and liquid contact is extremely small 'as the surface of the trickle 'of liquid rei'rigerant flowing through the evaporator amounts to but a small fraction of the interior surface area of the evaporator conduit. This arrangement produces an inemcient apparatus because heat transfer between the inert gas and the metal wall of the evaporator conduit is poor and the area of the conduit which is wetted by the liquid is small as noted above, wherefore in emcient evaporation results and a sharp temperaturediflerentlal is maintained between the exterior wall di the evaporator and the gas stream flowing 'therethrough In -addition to*the above factors the gas stream is discharged from the evaporator at a very low temperature which rep.

'resents'just so much wasted ref'rigerative elfort.

various means have been utilized in an attempt 4 to remedy this condition but au` of these means cause additional compications in the amratus and 'are only indiiferently successful. Among such means may be 'mentioned the provisicn of wicking material in the evaporator. the insertion of metal wires and the insertion'of metal rlbbons.

These devices tend to dlstribute' the liquid refrigerant butthey impede the flow 'of the inert gas, require a larger conduit, add very greatly to the cost of the evaporator and they form an additiona link in the path through which the heat' is conducted from the exterior walla of the-s u evaporator to the liquid reirigerant therein contalnd. The' net result ofthese-constructions is that the additional. length of the heat conducting path and the additional flow resistance 'prac -tically 'oifsets the advantages gained"byenlarging the .area of the liquid refrigerant in contact with -theinert gas. i

Accordingly, it is a principal objectef the present invention ,to provide an evaporat'or in which an unbroken film of. liquid refrlgerant is maintainedunuormlythroughout the et'ent of ,the

evaporator upon and across which the inertgas flows'whereby to provide direct liquid 'to metal tinuously 'remove accumulated strong solution spaced of in contact with a A I thin of-- liquid which adher'ee' to the entire heat tranu er throughout the entire extent of 5 innerwall of the evaporator conduit.

the e'vapo'rator wan and also to provide the maximuni possible gas and liquid heat contact area without the introduction of'any structura elements intothe interior of the evaporator conduit which would tend to impede the heat transfer v or to interferewiththe gas flow there'through.

4 It is another object of the invention to provide a three-fluid absorption refrigerating system r in'` which the iquid refrigerant circulates through the evaporator by gas lift action in contact wtih v the gas into which it evaporates.

It is another-..object of the present invention to provide a three-fluid'absorption refrigerating system in which the liquid refrigerant is circu-` lated through an evapora'tor having a pair of disa ti'nctsections by twin gas lift pumping action.

It is a further object of the present invention i to provide'a three-fluid 'abso'rption refrigerating system with an evaporator conslsting of a pair of parallel connected substantially identical or, if

preferred, non-identical sections through which the limid refrigerant is'circuated by gas lift action and-'in which the two, sections of the eYaD- oratorconduit operate on the twin gas lift -pump principle. 4

; It is -a further object of the invention to pro- 1 vide a three-fluid abscrption refrigerating sys- 'tem including an evaporatorwhich is practically independent of the'elevation at which the condenser' is located.

` It is another object of the invention to' provide a refrigerating system in whih a very large body oi cold liquidrefrigerant is continuousy circu'- lated through the evaporatlng portion of the apparatus. i v It is another object ofthepreent invention to .provide a three-fluid absorption refrigerating system in which foreign iodies,` such as absorption solution flndingthei; way intothe evaporator are continuousiy removed therefrom.

- It is a further object of the present invention to 'provide 'a three-fluid abcrptionrefrigerating system including an evaporato'r Operating on the gas' liftpump principle and including a reiatively large body of liquid refrigera t which is recircusl ated through the; evaporator v h means to confrom'the re-circulating material.

It is a-still further object of thepresent in- 'vention to' provide a three fluid absorptlon refrlgerating system in 'whichspaced bodies of gas circuate through the operator alter'natihg with able heating means,

. pumping gas to the conduit i'l.

tion ot the solution reservoir S is vented by means ot a small conduit 20 to the conduit ZI which is connected directly to the suction side of the cir- Other objects and advantages 'of the inventi'onwill become apparent as the description proceeds when taken in connectionwith the accompanying drawing, in which the single figure of D, an air-cooled rectifler R, a tubular air-cooled condenser C, an evaporator E, a gas heat exchanger G, an inclined tubular air-cooled 'absorber A, a liquid heat exchanger L, a solution reservoir S, and a circulating fan F which is driven by an electrical motor M. These elements are suitably interconnected by various conduits to form a. complete rei'rigerating system including a number of gas and liquid crcuits to which reference will be made in more detail hereinafter.

The above mentioned refrigerating system will be charged with a suitable refrigerant, such as ammonia, asuitable absorbent therefor, such as water, and an inert pressure equalizing medium, preferably a 'dense inert gas like nitrogen.

The boiler B may be provided' with any suitsuch as an electrical cartridge heater, a gas burner or a liquid fuel burner.

The application of heat to the boiler B generates refrigerant vapor from the refrigerant absorbing solution therein contained. The vapor "so generated passes upwardly through the analyzer D in counterflow to strong solution flowi'g downwardy therethrough whereby further reirlgerant vapor is generated by the heat of condensation of absorption solution vapor carried into the analyzer. The refrigerant vapor is changer L and a. flnned pre-cooling conduit IS. The liquid level prevailing in the boiler-analyzer reservoir system is appreciably below the -upper g portion of the absorber wherefore a gas lift pump conduit l'l isprovided to convey the lean solution rrom the bottom portion of the reservoir S into 'the upper portion of the absorber A. A small gas bl'eed conduit: !8 is connected between the discharge conduit s of thecirculating fan F and the gas lift pump i'l below the liquid level normally. prevailing therein in order to supply culating fan :Ehwhereby the gas lift pump is enabled to operate with-the maximum pressure diri'erential 'available'in the system.

The lean solution supplied to'the absorber A flows downwardly therethrough 'by-V gravity in counterflow relationship to a mixture of pressure equa'lizing medium and retrigerantv'apor which 'flows upwardly therethrough and is supplied !rom the evaporatonj The solution absorbs the retrigerant vapor contnt 'ot the 'n'ixture and the The upper pora ing across the fins provided on the exterior walls i of the absorber conduit;

The strong solution which is formed in the absorber as a result of the absorbing action flows to the bottom portion thereof from which point it is conveyed to the upper part of the analyzer D by way of the conduit 23, 'the liquid heat ex- Changer L, and the conduit 25.

The lean inert gas formed in the absorber is 1 0 conveyed from the upper end thereof through the pipe z into the suction side of the circulating fan F in which it is placed under pressure and is discharged through the conduit IB into the outer path of the gas heat exchanger G i'rom which the lean gas is conveyed by means ot the conduit 26 into the bottom portion of the evaporator E. r

The refrigerant vapor which is supplied to the condenser C by way of the conduit ll is liquefled in the condenser and is discharged thereirom into a reservoir and separation vessel 28 by means of a conduit 29. The liquid refrlgerant is conveyed from the reservoir into the bottom portion of the evaporator in a manner to be described in more detail hereinafte'r. `For the 30 rator E also includes an upper flnned tubular box-cooling section 30 which discharges into the vessel 28. The rich gas is then conveyed from the vessel 28 to the inner path of the gas heat exchanger G by means of .the conduit 31 and lis 35 'conveyed 'from the inner path of the gas heat exchanger G to the bottom portion oi' the ab'- sorber` A by means ot the conduit 32. The inert gas refrigerant vapor mlxture flows upwardly through the absorber A in counterflow to the 40 absorptionsolution in the manner heretofore described.

"- Specifically considered, the evaporator E comprises a pair of similar sections which are formed of a continuous piece of tublng or of a plurality of pre-formed sections of tubing which are suitably Joined as by welding. As illustrated, the evaporator comprises a right-hand section !I and a left-hand section 36. As these 'two sections of the evaporator are identical, a description* of one will sufllce for a description of both. Re-

ferring now to the right-hand section 35 of the evaporator the same comprises a pair of lower and upper rearwardly directed horizontal parallel U-shaped conduits 38 and 39, respectively.

which are connected at their rear outer sides by means of a riser conduit 40. The inner leg of the U -shaped conduit 39 'is connected to a V single overlying forwardly directed conduit ll by means of a riser 42. The forward enioi' the conduit ll is connected by a short riser 43 into the box-cooling conduit 30 and on the right hand side of a central partition u. The upper end of the evaporator section !i terminates on the adapted when enclos edin a suitable casing to support ice trays or ice tray supporting shelves in order toproduce low temperature refrigeration. The conduit ll will also aid in rerrigerating material supported upon the coils ll.

The inner bottom legs of the U-shaped conduits u o! the coil sections :I and u are eheat or absorption'isrejectedtooooling air i iow- 7 rially cted by a u-shaped conduit u which i ofthepartitionu., e'

" Ithas been found lo'g experience in operating the type of system heroin disclosed that an inverted U-shaped conduit ll which is connected to the inert gas supply conduit II.

, v me a extends downwardly below the plane of the con- -duit ll'a .slight distance. Each leg of the -U-shaped conduit u is connected to one end of The liquid tef'iterant which accumulates in i the vessel !I is conveyed therefrom into the bight portionof the 'conduit fl by means 'of'a conduit II which extends into the vessel !I and termi;

nates in a downwardly facing goose-necked end I portion li at approrimately the mld point of the vessel Il. 'i'he vessel 20 includes .a trapping and separation cup' li positioned adjace'nt the discharge point 'of the box-cooling conduit u inorde'r to receive liquid refrigerant fiowing therethrough. -A conduit u is arranged to convey liquid material supplied to the'cup !I in the vessel !I by the box-cooling conduit ss to thebottom portion' of the vessel II.

The evaporatorrand ment II upwardly about three-fourths of theverticai height thereof and then turns rear- 'wardly 'as viewed in the drawing. .passing .through the rear wall of the vessel II. after which the bottom of the containing-vasal. 'This phenomena is fscilitated if the conditions prevailing in 'the vessel are relatively static. 'The present invention takes advantage of this phenomena by 'returning the solution which is circulated through the evaporator directly to the bottom portion of the vesse :s andby directing the ,fresh solution through the conduit I! at a point relativeiy adiacent the bottom portion ofthevessel Il. Absotption solution which finds its way into the evaporator iscontinually returned to' the bottom portion of the vessel II by the con:-

duit II. '1'he goose neck llwfeedsrefrigerant liquid rising from the bottom of the vessel 'andsupplied -from the conduit I! whichhasna very low sbsorption evaporator.

v the U-shaped conduit 41` may be constructed either' from a continuousi piece of tubing bent to a suitable shape or it may be' contructed from a pluraiity of pre-formed The twir'' gas lift pump per se is disclosed and claimed in the co-pending application of 0.' Coons and Rudolph S. Nelson. serial No. 169;- 986, mea October 20th, 1937. It is characti'lstic of this type oi pump that there is provided an oscillating column of liquid in the bight portion of the U.-shaped'conduit 41. This oscillatihg body.

. the condui't il extends downwardly'and -terminates in communication with the rich solutiorj return conduit 23, A small vent conduitll opens into-'the Whst portion of the conduit .I which is within the vessel Il and terminates in the 'upper gas containing portion of the vessel 20.'

The 'apparatus will be charged with a-refrigerant absorbent and inei't 'gas in the usual man.-

ner with 'the following exceptions. The vessel of liquid isbeieved to be argely responsible for the remarkable emciency of the 'twin gas lift Dumb.

in a b'road sense. the liquid refrigerant -is circulated through the evaporator'by gas lift action; that is'. the low density column of gas and-liquid in the evaporator conduit. the' punu) portion per se. is balanced bythe relativelyhigh 'density solid column of liquidin the storage vesselnd the liquidsuoply oonnections therefron to` theevaporaton In this application the term g "gas li! is to be construed as' meaning a pumpor 'elevating mechanism Operating in the mani ner described immediately above.

!I will be charged directly with 'liquid refrigerant up to approximately the. level of the point of connection between the conduits !I and` 02.

The operation of the invention except as the same has been described hereinabovevis asfallows: When the appara'tus is initially charged' theliquid refrigerant stands' in the vessel :I .ne.

in; the evaporator :Eat a 'level corresponding spproximately-to the'- level of the point'ot connection between the conduits ti and u. when' the control mechanlsm 'ehergizes the heater for the boiler and the electrical motor M, inertas is supplied to' the U-sha' d conduit "through the conduit ll; --The` thus supplied alter nately dischargcs from -tlie legs of the Usshaped .A 'twin'gas lift pump or twin gas lift action diiierslfrom the more conventional simple gas .iftpump orsimple gas lift action in that there are two gas lift pumping conduits per se which are Joined to each other in a manner to provide achamber filledwith liquid. which liquid will osoillatebetween the two 'pumping columns per seas pumping gas 'is "applied to these columns.

. arrangement.

-It is this oscillating body or 'pisten of liquid which is believed to be primarily responsibieflfor the remarhable emciency of the twin gas lift ar- -rangement as compare'd with a simple ga's' lift Due to the fact that the fresh liquid refrigerant supplied from the oonduit- :I and the recirculated liquid refrigerant ilowing through the tion of the vessel II, the liquid that'bottom oonduit s into the legs the U-shaped conduits j r si which are connected with the evaporatorssctions :I and I! and the liquid refrigerant there.. in is eleaated therethroul by twi'n gas iiftlac tipn, 'that is, a slugof gas alternatey enters the right 'and left hand sides of the U-shaped con duit 41 whereby the liquid refrigerant will,di`s- .charge. from the evaporstbr 'sections ;l'nd :I

alternately 'into the conduit ll on-opposite sides small quantities of absorptionrsolution will find 'theirwy ntothe evaporator and that these must water a greater density than a weakrsoluoonduit Il -each flow directly tothe bottom porportion of 'the vessel contains the largest percentage' of the heavier absorption solution and the liquid in the upper portion of the vessel !i 'contains relatively pure liquid refrigersn't.

- .Therefore. there isa continual though very slovremoval of solution 'from the bottom portion oz -the vessel ss through the cond it s into tul a strong solution return line II.. Thisarrangemen' prevents the con'oentration of absorption soiu tion in the liquid circulating through the evaporator and vessel `!0 from teaching a value sufficiently high to interfere with proper evaporai tion and production of refrigeration; Also the arrangement including' the conduit i. prevents the-liquid level within the vessel 2! from reaching toohigh 'a level.

The liquid whichis continuously circulating ther'eof-or than pure ammonia and in'such through the evaporator becomes very cold where- I the. strong solution tends to settle-at 15 fore the contents of the vessel zl are very cold solution concentration into the ment. This prevents a decrease in the efliciency of the system by warming' of 'the body of liquid contained in the vessel 28, which in eifect acts v as a cold accumulator for the entire system.

The liquid rei'rigerant and inert gas circulates through each section of the evaporator by gas ift action; that is alternate slugs of gas and liquid travel upwardly through the evaporator portions 35 and 36 from the U-shaped conduit 41 to the conduit 30. As a result of this action each slug of liquid leaves a thin film of liquid refrigerant along the wall of the evaporator conduit which liquid of course immediately partially evaporates into the succeeding body of inert gas. Thus refrigerationis produced by evaporation of a thin film of liquid refrigerant which covers the entire inner wall of the evaporator conduit directly into a stream of inert gas flowing through the evaporator.

This thin continuous film of liquid with which the gas is' in intimate and continuous contact is provided without' introducing any structure .of any nature into the interier of the evaporator 'and without introducing therein anything which would' tend to impede heat transfer or free flow of gas and liquid therethrough.

D ue to' the fact that the liquid refrigerant is supplied to the bottom portion of the evaporator' and is elevated therethrough by the inert gas the relative position of the evaporator E and of the condenser C are independent within practical limits. For example, it is not necessary that the upper portion of the condenser be' positioned at an elevation above the upper portion of the evaporator; On the contrary the condenser C may extend substantially to the level of the bottom portion of the vessel 28 which` is only slightly higher than the bottom portion of the U-shape conduit H.

All fluids in the system are circulated by the inert gas; that is, the absorption solution is circulated by the gas lift pump I'I and the liquid refrigerant is circulated through the evaporator by twin gas lift action, thereby assuring that the rates of circulation of all fluids in the system willbe properly proportioned relativeto each other and relative to the rates with which the' inert gas is circulated.

By providing a twin gas lift pump arrangement in the evaporator the eflicieney of the apparatus is greatly enhanced and the design of the-evaporator is rendered relatively fiexible. It is characteristic of this type of pump or circulator that Accordingly there is provided an absorption refrigerating system in which all fluids are circulated by gas lift action, in which provision is' made for a continuous purge of ,the evaporator system to relieve the same of foreign materials such as absorption solution and in which evaporation occu-s 'from a thin continuous film of refrigerant covering the entire inner surface of the evaporator. There'is a direct heat transfer between the wallof the evaporator and the liquid unser refrigerant without the intervention of any interior construction in the evaporator and without impeding the flow of gas' and liquid therethrough. Another feature of the invention resides `in the fact that the large cold body of liquid refrigerant which is present in the evaporator and in the storage purging vessel has a stabilizing influence on the system and tends to sreduce the frequency of the operative periods of the apparatus when the same is operated as an intermittent cycle system.

Though the invention has been illustrated and described in considerable detail, it is not to be construed as being limited thereto as various changes may be made in the construction, proportion, arrangement of parts without departing from the spirit of the invention or the scope of the appended claims.

I claim:

l. Refrigerating apparatus comprising a cooling unit including a pair of individual sections, each of said sections being" connected to each other and to a common source of supply of cool- -ing medium, and common means for introducing an inert gas into the cooling medium supplied to each of said sections to circulate the cooling medium therethrough by twin gas lift action.

2. Absorption refrigerating apparatus compris-' twin gas lift pump for the circulation of liquidrefrigerant therethrough.

3. Absorptionrefrigerating apparatus comprising a solution circuit including an absorber and a boiler, a pressure equalizing medium circuit including an evaporator, a storage vessel and said absorber, means for liquefying refrigerant vapor generated in said boiler, means for circulating the pressure equalizing medium through said *pressure equalizing medium circuit, said evaporator comprising a pairiof parallel connected continuous conduits, said storage vessel being connected to the inlet and outlet portions of each of said evaporator conduits and arranged to hold a quantity of liquid refrigerant, means.

for supplying liquid refrigerant from said storage vessel andfrom said liquefying means to a portion of said' evaporator common to each of said conduits, and common means in said preseach of said parallelconnected evaporator con-- sure equalizing medium circuit for introducins pressure equalizing medium into the portions of 4. Absorption refrigerating apparatus comprising a solution circuit includingan absorber and a boiler, a pressure equalizing medium circuit including an evaporator, a storage vessel and said absorber, means for liquefying refrigerant vapor generated in said boiler, means for circulating the pressure equalizing medium through said pressure equalizing medium circuit; said evaporator comprising a pair of parallel connected continuous conduits, said storagevesse'l being arranged to hold a quantity of liquid refrlcerant and being connected to the inlet and outiet portions of each of said evaporator con'duits, means' for s'upplying liquid refrigerant from said vessel and from said liquefying means to each of said evaporator conduits, means in said presente equalizing medium circuit for 'introducing pressure equalizing medium into the portion of each of said conduits which is supplied with' refrigerant liquid, whereby the same will operate as a twin gas lift pump to circulate liquid refrigerant including an m i nama smi havlns oneend terminating within said vessei adiacent the bottom thereof and its other end connected to'sald solution .circuit. and `means venting the e bight portion of said U-shaped conduit to the sto age vessel having its' upper and lower porfrom said storage vessel, and means for continu'- n ously conveying a small quantity of liquid from the bottom portion of saidstorage vessel into another portion of the system normally contain-.

ing liquid refrigerant.

- 5. Refrigerating apparatus including an evaporator comprising a pair of continuous 'condults shaped to form a plurality of horizontal coils, a

' U-shapedconduit connected to the bottom portion of each of said evaporator conduits, means for supplying liquid refrigerant to the bight pora tion of said U-shaped conduit; and common means for'introducing inert gas into the rising portions of each leg of said U-shaped conduit.

tions connected to the upper and lower portions respectively of said evaporator, means for sup-' plying refrigerant vapor produced in said gen-.

, /er'ator to said vessel in liquidphase. a power 6. Refrigerating apparatus comprising a tubular evaporator including a pair of individual sections, a U-shaped conduit connected to the inlet portion of each of said sections, a storage and re-circulation vessel connected to the upper out- 'let portion of each of said evaporator sections,

a U-shaped liquid seal conduit to convey liquid from said vessel into the bight portion of said U-shaped conduit, an inverted U-shaped con- .duit connected 'to each of the legs of said nrst-mentioned' U-shaped conduit. means for introducing an inert gas into the bight portion of saidinverted U-shaped conduit, means within said vessel for separa'ting gas and liquid supplied' thereto from the upper ,portion of said' evaporator'. means for removing gas from said separation vessel, and means for supplying fresh liquid thereto. i y

'1. Refrigerating apparatus I lar evaporator, a liquid refrigerant supply means. a vessel connected to each end of said evaporator comprising a tubuand to .said llquid refglgerant supply means` and arranged to supply liquidrei'riserant to said evaporator, means for introducing an' inert gas into the liquid refrigerant supplied to said evav rator to circulate the liquid refrlgerant therethrough by gas lift action, and means for-substantially continuously removing material from' the' bottom portion of said vessel into. said liquid rei'rigerant sunply means. i

8. Absorption refrigerating apparatus comprisi ing an inert gas circuit including an absorber, a circulation and storage vessel and an upstanding evaporator conduit, a solution circuit including a generator and said absorber, said circulation and storage vessel having its upper and lower portions connected to the' upper and lower portions respectively .of said evaporator conduit, means for supplying refrigerant vapor produced in said generator to said vessel in liquid phase. said ine't gas circuit being so constructed, and arranged that the inert gas is introduced into said evaporator conduit in a manner, to circulate the liquid refrigerant therethrough by gas lift action, and means for drainleg thereof connected to the lower end of one'of' ing the materialat the extreme bottom portion r I predetermined value, saidlast mentioned means u ingthe material at the extreme bottom driven means for circulating the inert gas through said inert gas 'circuit in such fashion that the liquid refrigerant'is circulated through said evaporator thereby. syphon means for drainq n of said vessel into said solution circuit whenever the level of the liquidinsaidvessei exceeds a predetermined value, and means for venting saidsyphon means to theuppe' gas-containing portion of said vessel in' such fashion that said eyphon means will cease to function immediately the lquidjle'vel in said vessel is reduced below said predetermined value.

'10. Refrgerating apparatus comprising a of'evaporatorsconstructed of unobstructed coni duits, 'means providing for free*and un'obstructed communication between said evaporators 'at the lower ends thereof. a source' of supply of refrlgerant common to each of said evaporators. means for introducing a pressure equaliaing medium into the'liquid refrigerant in each of said* evaio-` rators to raise therefrlgerant therethroush br twin' gas lift actiohwhereby the gas nowa through of said evaporators in contact with nm of of. v

the refrigerant on the inner walls there- 11."'Absorptlon apparatus comprising a solution cireuit including a generator and an absorber, a pressure equalizing medium circuit including said absorber, a pair 'of evaporators constructed of unobstruct'ed condlits in free and open communication at their lower ends and to a flnned evaporator at their upper ends and awessel having open communication with the connected ends of said n pair of evaporators at its lower end and with said finned evaporator`.at its upper end, and power driven means for propellingthe pressure equaizing medium through its -circit, said p-essu'e` equalizin'g medium circuit including means for introducing pressure equalizing medium into that `portion of each of said pair of evaporators to which liquid refrigerant is supplied 'whereby the refrigerant' is circulated therethrough by twin gas liftactiony -4 n 12. Refrlgerating apparatus comprising a cooling unit including a pair of like 'sectionseach of which is constructed of tubing'shaped to form a `plurality of shell-lige sections serialiy connected by ris'er'secticns. a U- shap'ed conduit having each cooling medium through said cooling unit bx gas lift action.

13. Absorptlon refrigerating apparatu's comprising an absorber, and a pairof upstanding con'- means !or conveying gas and liquid which has 'traversed said evaporator conduts to 'said aba.

whenever' the level of the liquid in said vessel xceeds a predetermined value.

14. Rei'rlgerating apparatus comprising a cool ing unit including a pair of sections' in open communication with each other at one end thereof, means for supplying a cooling medium to the communicating ends of said sections, and means for introducing an inert gas into each of said sections adjacent the communicating ends thereof to circulate the cooling medium therethrough by twin gas lift action, said means for introducing inert gas into said sections. being soconstructed serbet and said vessel, respectively, and means for draining the material at the extreme bottom portion of said ,vessel into said solution circuit and arranged that open communication is provided between each of said sections through said 15 inert gas introducing means.

ALFRED G. GROSS. 

